Semiconductor relay control device

ABSTRACT

An FET makes an upstream power supply circuit an energized state and makes the upstream power supply circuit an interrupted state. An FET makes a downstream power supply circuit an energized state and makes the downstream power supply circuit an interrupted state. An FET turns on to make an anode and a cathode of the capacitor an energized state, and turns off to make the anode and the cathode an interrupted state. A controller turns on the FET and the FET and turns off the FET to make a power supply circuit an energized state. When a certain discharge request is input in the energized state of the power supply circuit, the controller turns off the FET and turns on the FET and the FET. With this configuration, a semiconductor relay device can appropriately address the power supply circuit at the time of abnormality.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of InternationalApplication PCT/JP2018/026845, filed on Jul. 18, 2018 which claims thebenefit of priority from Japanese Patent application No. 2017-215314filed on Nov. 8, 2017 and designating the U.S., the entire contents ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a semiconductor relay control device.

2. Description of the Related Art

Electric vehicles or hybrid electric vehicles have conventionally beenequipped with a power supply circuit having a high voltage load partsuch as an inverter and a high voltage battery for driving the highvoltage load part in some cases. This power supply circuit is providedwith an interrupting circuit passing or interrupting a current passingfrom the high voltage battery to the high voltage load part for thepurpose of security. Although mechanical relays are often used for thisinterrupting circuit, in recent years, semiconductor relays have beenused in some cases (e.g., Japanese Patent Application Laid-open No.2016-092962).

The interrupting circuit of Japanese Patent Application Laid-open No.2016-092962 described above may become a state in which electric chargesare charged to a capacitor of the high voltage load part at the time ofabnormality such as a vehicle collision, for example, and thus there isroom to further improve in this regard.

SUMMARY OF THE INVENTION

Given these circumstances, the present invention has been made in viewof the above, and an object thereof is to provide a semiconductor relaycontrol device that can appropriately address the power supply circuitat the time of abnormality.

In order to solve the above mentioned problem and achieve the object, asemiconductor relay control device according to one aspect of thepresent invention includes an upstream semiconductor relay connected, inan upstream power supply circuit, in a circuit in which a load partincluding a capacitor and a DC power supply are connected to each other,the circuit being a power supply circuit in which the capacitor isconnected in parallel to the DC power supply, between a positiveelectrode of the DC power supply and the load part, in series to betweenthe positive electrode and the load part, turning on to make theupstream power supply circuit an energized state, and turning off tomake the upstream power supply circuit an interrupted state; adownstream semiconductor relay connected, in a downstream power supplycircuit between a negative electrode of the DC power supply and the loadpart, in series to between the negative electrode and the load part,turning on to make the downstream power supply circuit an energizedstate, and turning off to make the downstream power supply circuit aninterrupted state; a semiconductor relay for discharge connected inparallel to the capacitor, turning on to make an anode and a cathode ofthe capacitor an energized state, and turning off to make the anode andthe cathode an interrupted state; a diode that is provided so as to havea current passing direction opposite to a direction in which a currentpasses from the DC power supply to the load part and is connected inparallel to the semiconductor relay for discharge; and a controllercontrolling the upstream semiconductor relay, the downstreamsemiconductor relay, and the semiconductor relay for discharge, whereinthe controller turns on the upstream semiconductor relay and thedownstream semiconductor relay and turns off the semiconductor relay fordischarge to make the power supply circuit an energized state and, whenthe power supply circuit is short-circuited, the controller turns offthe upstream semiconductor relay and the semiconductor relay fordischarge and turns on the downstream semiconductor relay, a negativesurge voltage caused by the turning off of the upstream semiconductorrelay is clamped by the diode.

According to another aspect of the present invention, in thesemiconductor relay control device, it is preferable that when a certaindischarge request is input in the energized state of the power supplycircuit, the controller turns off the upstream semiconductor relay andturns on the downstream semiconductor relay and the semiconductor relayfor discharge.

According to still another aspect of the present invention, in thesemiconductor relay control device, it is preferable that the controllercontrols the semiconductor relay for discharge to regulate a currentpassing through the semiconductor relay for discharge.

In order to achieve the object, a semiconductor relay control deviceaccording to still another aspect of the present invention includes anupstream semiconductor relay connected, in an upstream power supplycircuit, in a circuit in which a load part including a capacitor and aDC power supply are connected to each other, the circuit being a powersupply circuit in which the capacitor is connected in parallel to the DCpower supply, between a positive electrode of the DC power supply andthe load part, in series to between the positive electrode and the loadpart, turning on to make the upstream power supply circuit an energizedstate, and turning off to make the upstream power supply circuit aninterrupted state; a downstream semiconductor relay connected, in adownstream power supply circuit between a negative electrode of the DCpower supply and the load part, in series to between the negativeelectrode and the load part, turning on to make the downstream powersupply circuit an energized state, and turning off to make thedownstream power supply circuit an interrupted state; a semiconductorrelay for discharge connected in parallel to the capacitor, turning onto make an anode and a cathode of the capacitor an energized state, andturning off to make the anode and the cathode an interrupted state; aprecharge circuit having a series circuit in which a resistor and asemiconductor relay for precharge are connected in series to each other,the series circuit being connected in parallel to the downstreamsemiconductor relay, passing a current through the series circuit by theturning on of the semiconductor relay for precharge, and not passing anycurrent through the series circuit by the turning off of thesemiconductor relay for precharge; a diode that is provided so as tohave a current passing direction opposite to a direction in which acurrent passes from the DC power supply to the load part and isconnected in parallel to the semiconductor relay for discharge; and acontroller controlling the upstream semiconductor relay, the downstreamsemiconductor relay, the semiconductor relay for discharge, and thesemiconductor relay for precharge, wherein the controller turns on theupstream semiconductor relay and the downstream semiconductor relay andturns off the semiconductor relay for discharge and the semiconductorrelay for precharge to make the power supply circuit an energized stateand, when the power supply circuit is short-circuited, the controllerturns off the upstream semiconductor relay and the semiconductor relayfor discharge and turns on the downstream semiconductor relay, anegative surge voltage caused by the turning off of the upstreamsemiconductor relay is clamped by the diode.

According to still another aspect of the present invention, in thesemiconductor relay control device, it is preferable that when a certaindischarge request is input in the energized state of the power supplycircuit, the controller turns off the upstream semiconductor relay andthe downstream semiconductor relay and turns on the semiconductor relayfor precharge and the semiconductor relay for discharge.

The above and other objects, features, advantages and technical andindustrial significance of this invention will be better understood byreading the following detailed description of presently preferredembodiments of the invention, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a configuration example of asemiconductor relay control device according to a first embodiment;

FIG. 2 is a timing chart of an operation example (normal stopping) ofthe semiconductor relay control device according to the firstembodiment;

FIG. 3 is a circuit diagram of an operation example (a dischargeoperation) of the semiconductor relay control device according to thefirst embodiment;

FIG. 4 is a timing chart of the operation example (the dischargeoperation) of the semiconductor relay control device according to thefirst embodiment;

FIG. 5 is a diagram of a relation between a gate-source voltage and adrain current according to the first embodiment;

FIG. 6 is a circuit diagram of an operation example (a short circuitoperation) of the semiconductor relay control device according to thefirst embodiment;

FIG. 7 is a timing chart of the operation example (the short circuitoperation) of the semiconductor relay control device according to thefirst embodiment; and

FIG. 8 is a circuit diagram of a configuration example of asemiconductor relay control device according to a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following describes modes (embodiments) for performing the presentinvention in detail with reference to the accompanying drawings. Thedetails described in the following embodiments do not limit the presentinvention. The following components include ones that those skilled inthe art can easily think of and substantially the same ones.Furthermore, the following configurations can be combined with eachother as appropriate. Various omissions, replacements, or modificationsof the configurations can be made without departing from the gist of thepresent invention.

First Embodiment

The following describes a semiconductor relay control device 1 accordingto a first embodiment. A vehicle such as an electric vehicle or a hybridelectric vehicle is provided with a high voltage system 100 supplyingpower supply power from a high voltage battery 2 to a high voltage loadpart 3 to drive the high voltage load part 3, for example. This highvoltage system 100 includes the high voltage battery 2 as a DC powersupply, the high voltage load part 3 as a load part, and thesemiconductor relay control device 1. The high voltage system 100 formsa power supply circuit 101 in which the high voltage battery 2 and thehigh voltage load part 3 are electrically connected to each other viathe semiconductor relay control device 1.

The high voltage battery 2 is a chargeable/dischargeable high voltagesecondary battery and includes a lithium-ion battery pack or anickel-hydride battery pack including a plurality of batteries connectedto each other, for example. The high voltage battery 2 has a terminalvoltage of a few hundred volts, for example. The high voltage battery 2is connected to the high voltage load part 3 via the semiconductor relaycontrol device 1 to supply power to the high voltage load part 3.

The high voltage load part 3 is a high voltage load part and is aninverter, which converts a direct current into an alternating current tosupply power to a drive motor, for example. The high voltage load part 3is connected to the high voltage battery 2 via the semiconductor relaycontrol device 1. The high voltage load part 3 has a capacitor C, andthe capacitor C is connected in parallel to the high voltage battery 2.The high voltage load part 3 converts DC power supplied from the highvoltage battery 2 into AC power and supplies the AC power to a drivemotor, for example.

The semiconductor relay control device 1 is an interrupting device (apower supply box) passing or interrupting a current passing from thehigh voltage battery 2 to the high voltage load part 3 for the purposeof security. The semiconductor relay control device 1 performs prechargecontrol to pass a precharge current through the power supply circuit 101in order to prevent a rush current into the high voltage load part 3.After the precharge control, the semiconductor relay control device 1passes a current larger than the precharge current through the powersupply circuit 101. As illustrated in FIG. 1, the semiconductor relaycontrol device 1 includes a field-effect transistor (FET) 11 as anupstream semiconductor relay, an FET 12 as a downstream semiconductorrelay, a driver 21, a driver 22, a current detector 30, a prechargecontroller 40, an FET 13, and a controller 50.

The FET 11 is a switching element passing or interrupting the currentpassing from the high voltage battery 2 to the high voltage load part 3.The FET 11 is provided in an upstream power supply circuit 101 a betweena positive electrode of the high voltage battery 2 and the high voltageload part 3. The FET 11 is connected in series to between the positiveelectrode of the high voltage battery 2 and the high voltage load part3. The FET 11 is an N-channel type metal-oxide-semiconductor (MOS) FET,for example. The FET 11 has a gate terminal, a drain terminal, and asource terminal. The gate terminal of the FET 11 is connected to thedriver 21, the drain terminal thereof is connected to the positiveelectrode of the high voltage battery 2, and the source terminal thereofis connected to the high voltage load part 3. In the FET 11, an ONvoltage is applied to the gate terminal, whereby a current (also calleda drain current) passes between the drain and the source. In the FET 11,an OFF voltage is applied to the gate terminal, whereby no currentpasses between the drain and the source. In the FET 11, a body diode (aparasitic diode) D1 is arranged in an orientation opposite to adirection in which the current (the drain current) passes. A cathodeterminal of the body diode D1 is connected to the drain terminal of theFET 11, whereas an anode terminal thereof is connected to the sourceterminal of the FET 11. The FET 11 is driven by the driver 21 describedbelow to turn on, thereby making the upstream power supply circuit 101 aan energized state and thus passing a current from the positiveelectrode of the high voltage battery 2 to the high voltage load part 3.The FET 11 is driven by the driver 21 to turn off, thereby making theupstream power supply circuit 101 a an interrupted state and thusinterrupting the current passing from the positive electrode of the highvoltage battery 2 to the high voltage load part 3.

The FET 12 is a switching element passing or interrupting a currentpassing from the high voltage load part 3 to the high voltage battery 2.The FET 12 is provided in a downstream power supply circuit 101 bbetween a negative electrode of the high voltage battery 2 and the highvoltage load part 3. The FET 12 is connected in series to between thenegative electrode of the high voltage battery 2 and the high voltageload part 3. The FET 12 is an N-channel type MOSFET, for example. TheFET 12 has a gate terminal, a drain terminal, and a source terminal. Thegate terminal of the FET 12 is connected to the driver 22, the drainterminal thereof is connected to the high voltage load part 3, and thesource terminal thereof is connected to the negative electrode of thehigh voltage battery 2. In the FET 12, an ON voltage is applied to thegate terminal, whereby a current passes between the drain and thesource. In the FET 12, an OFF voltage is applied to the gate terminal,whereby no current passes between the drain and the source. In the FET12, a body diode D2 is arranged in an orientation opposite to adirection in which the current (the drain current) passes. A cathodeterminal of the body diode D2 is connected to the drain terminal of theFET 12, whereas an anode terminal thereof is connected to the sourceterminal of the FET 12. The FET 12 is driven by the driver 22 describedbelow to turn on, thereby making the downstream power supply circuit 101b an energized state and thus passing a current from the high voltageload part 3 to the negative electrode of the high voltage battery 2. TheFET 12 is driven by the driver 22 to turn off, thereby making thedownstream power supply circuit 101 b an interrupted state and thusinterrupting the current passing from the high voltage load part 3 tothe negative electrode of the high voltage battery 2. The FET 12performs control to pass the precharge current through the power supplycircuit 101 when the power supply circuit 101 is started up.

The driver 21 is a circuit turning on or off the FET 11. The driver 21is connected to the controller 50 and the gate terminal of the FET 11.When an upstream semiconductor drive signal (ON) is output from thecontroller 50, the driver 21 applies an ON voltage to the gate terminalof the FET 11 to pass a current between the drain and the source of theFET 11. When an upstream semiconductor drive signal (OFF) is output fromthe controller 50, the driver 21 applies an OFF voltage to the gateterminal of the FET 11 to interrupt the current passing between thedrain and the source of the FET 11.

The driver 22 is a circuit turning on or off the FET 12. The driver 22is connected to the controller 50 and the gate terminal of the FET 12.When a downstream semiconductor drive signal (ON) is output from thecontroller 50, the driver 22 applies an ON voltage to the gate terminalof the FET 12 to pass a current between the drain and the source of theFET 12. When a downstream semiconductor drive signal (OFF) is outputfrom the controller 50, the driver 22 applies an OFF voltage to the gateterminal of the FET 12 to interrupt the current passing between thedrain and the source of the FET 12. The driver 22 is further connectedto the precharge controller 40 and applies an ON voltage for prechargeto the gate terminal of the FET 12 based on control by the prechargecontroller 40 to pass the precharge current between the drain and thesource of the FET 12.

The current detector 30 is a detector detecting a current passingbetween the high voltage battery 2 and the high voltage load part 3. Thecurrent detector 30 is a Hall type current sensor including a Hallelement as a magnetoelectric conversion element, for example, anddetects a current in a noncontact manner. The current detector 30detects a current passing between the positive electrode of the highvoltage battery 2 and the FET 11, for example, and outputs the detectedcurrent (a detection current) to the controller 50 and the prechargecontroller 40. The current detector 30 may be a shunt type currentsensor, which detects a current based on a voltage drop occurring by theresistance of a shunt resistor, a VDS type current sensor, which detectsa current based on a voltage drop occurring in the FET 11, or the like.

The precharge controller 40 performs precharge control, which avoids arush current passing from the high voltage battery 2 to the high voltageload part 3. The precharge controller 40 performs precharge control oneither the FET 11 or the FET 12. In this example, the prechargecontroller 40 performs precharge control on the FET 12. The prechargecontroller 40 controls the gate voltage of the FET 12 to pass theprecharge current from the high voltage battery 2 to the high voltageload part 3. The precharge controller 40, upon start-up of the powersupply circuit 101, applies an ON voltage for precharge to the gateterminal of the FET 12 via the driver 22 to pass the precharge currentfrom the high voltage battery 2 to the high voltage load part 3, forexample. The precharge controller 40 passes a certain precharge currentonly during a period in which the capacitor C of the high voltage loadpart 3 is charged, for example.

The FET 13 is a switching element discharging electric charges chargedto the capacitor C. The FET 13 is connected in parallel to the capacitorC. The FET 13 is an N-channel type MOSFET, for example. The FET 13 has agate terminal, a drain terminal, and a source terminal. The gateterminal of the FET 13 is connected to the driver 23, the drain terminalthereof is connected to the anode of the capacitor C, and the sourceterminal is connected to the cathode of the capacitor C. In the FET 13,an ON voltage is applied to the gate terminal, whereby a current passesbetween the drain and the source. In the FET 13, an OFF voltage isapplied to the gate terminal, whereby no current passes between thedrain and the source. In the FET 13, the gate terminal, the drainterminal, and the source terminal function as a semiconductor relay fordischarge. In the FET 13, a body diode D3 as a diode is arranged in anorientation opposite to a direction in which the current (the draincurrent) passes. A cathode terminal of the body diode D3 is connected tothe positive electrode of the high voltage battery 2, whereas an anodeterminal thereof is connected to the negative electrode of the highvoltage battery 2. In other words, the cathode terminal of the bodydiode D3 is connected to the drain terminal of the FET 13, whereas theanode terminal thereof is connected to the source terminal of the FET13. The FET 13 is driven by the driver 23 described below to turn on,thereby making the anode and the cathode of the capacitor C an energizedstate and thus enabling the electric charges charged to the capacitor Cto be discharged. The FET 13 is driven by the driver 23 to turn off,thereby making the anode and the cathode of the capacitor C aninterrupted state and thus disabling the electric charges charged to thecapacitor C to be discharged.

The driver 23 is a circuit turning on or off the FET 13. The driver 23is connected to the controller 50 and the gate terminal of the FET 13.When a semiconductor-for-discharge drive signal (ON) is output from thecontroller 50, the driver 23 applies an ON voltage to the gate terminalof the FET 13 to pass a current between the drain and the source of theFET 13. When a semiconductor-for-discharge drive signal (OFF) is outputfrom the controller 50, the driver 23 applies an OFF voltage to the gateterminal of the FET 13 to interrupt the current passing between thedrain and the source of the FET 13.

The controller 50 controls the FET 11, the FET 12, and the FET 13. Thecontroller 50 includes an electronic circuit consisting principally of awell-known microcomputer including a central processing unit (CPU), aread only memory (ROM) and a random access memory (RAM) forming astorage unit, and an interface. The controller 50 is connected to thedriver 21 to control the FET 11 via the driver 21. The controller 50outputs the upstream semiconductor drive signal (ON) to the driver 21 toturn on the FET 11 and outputs the upstream semiconductor drive signal(OFF) to the driver 21 to turn off the FET 11, for example. Thecontroller 50 is connected to the driver 22 to control the FET 12 viathe driver 22. The controller 50 outputs the downstream semiconductordrive signal (ON) to the driver 22 to turn on the FET 12 and outputs thedownstream semiconductor drive signal (OFF) to the driver 22 to turn offthe FET 12, for example. The controller 50 is connected to a driver 23to control the FET 13 via the driver 23. The controller 50 outputs thesemiconductor-for-discharge drive signal (ON) to the driver 23 to turnon the FET 13 and outputs the semiconductor-for-discharge drive signal(OFF) to the driver 23 to turn off the FET 13, for example.

The controller 50 turns on or off the FETs 11 to 13 in accordance with arequest from an external device such as a host electronic control unit(ECU), for example. The controller 50 turns on or off the FETs 11 to 13based on a semiconductor drive signal (an external signal) output fromthis external device, for example. A semiconductor drive signal (ON) isa signal indicating turning on the FETs 11 and 12, whereas asemiconductor drive signal (OFF) is a signal indicating turning off theFETs 11 and 12. When the semiconductor drive signal (ON) is output, thecontroller 50 turns on the FETs 11 and 12 and turns off the FET 13 tomake the power supply circuit 101 an energized state, for example. Whenthe semiconductor drive signal (OFF) is output, the controller 50 turnsoff the FETs 11 to 13 to make the power supply circuit 101 aninterrupted state.

In addition, the controller 50 turns on or off the FETs 11 to 13 basedon a collision signal (an external signal) output from the externaldevice. A collision signal (collision) is a signal indicating that thevehicle has collided, whereas a collision signal (normal) is a signalindicating that the vehicle has not collided. When the collision signal(collision) is output, the controller 50 turns off the FET 11 and turnson the FETs 12 and 13 to discharge the electric charges charged to thecapacitor C, for example. When the collision signal (normal) is output,the controller 50 turns on the FETs 11 and 12 and turns off the FET 13to make the power supply circuit 101 an energized state, thus notdischarging the electric charges charged to the capacitor C.

In addition, the controller 50 determines a short circuit based on thedetection current output from the current detector 30. When determininga short circuit, the controller 50 turns off the FETs 11 and 13 andturns on the FET 12 to interrupt a short circuit current and to reduce anegative surge voltage caused by the turning off of the FET 11. When notdetermining a short circuit, the controller 50 turns on the FETs 11 and12 and turns on the FET 13 to make the power supply circuit 101 anenergized state.

The following describes an operation example (normal stopping) of thesemiconductor relay control device 1 with reference to FIG. 2. Thisexample assumes that in the high voltage system 100, the power supplycircuit 101 is in an energized state at a time t0. That is to say, inthe high voltage system 100, the FETs 11 and 12 turn on, the FET 13turns off, and an output voltage VL of the high voltage battery 2 is astationary voltage VH. In this case, when the semiconductor drive signal(OFF) is output from the external device, the controller 50 of thesemiconductor relay control device 1 outputs the upstream semiconductordrive signal (OFF) to the driver 21 to turn off the FET 11 and outputsthe downstream semiconductor drive signal (OFF) to the driver 22 to turnoff the FET 12 (a time t1). With this control, in the high voltagesystem 100, the power supply circuit 101 becomes an interrupted state,and the electric charges charged to the capacitor C self-discharge,whereby the output voltage VL of the high voltage battery 2 graduallydecreases from the stationary voltage VH to 0 V (the time t1 to a timet2). From the time t0 to the time t1, the high voltage system 100 turnson to make the power supply circuit 101 an energized state. From thetime t1 to the time t2, the high voltage system 100 turns off to makethe power supply circuit 101 an interrupted state.

The following describes an operation example (a discharge operation) ofthe semiconductor relay control device 1 with reference to FIG. 3 andFIG. 4. This example assumes that in the high voltage system 100, thepower supply circuit 101 is in an energized state at a time t0. That isto say, in the high voltage system 100, the FETs 11 and 12 turn on, theFET 13 turns off, and the output voltage VL of the high voltage battery2 is the stationary voltage VH. In this case, when the collision signal(collision) is output from the external device, the controller 50 of thesemiconductor relay control device 1 outputs the upstream semiconductordrive signal (OFF) to the driver 21 to turn off the FET 11 (a time t1).With this operation, the controller 50 makes the power supply circuit101 an interrupted state. The controller 50 then outputs thesemiconductor-for-discharge drive signal (ON) to the driver 23 at a timet2 after a lapse of a certain time from the time t1. The driver 23applies an ON voltage to the gate terminal of the FET 13 to turn on theFET 13 based on the semiconductor-for-discharge drive signal (ON). Withthis operation, as illustrated in FIG. 3, the controller 50 candischarge the electric charges charged to the capacitor C. With thisdischarge, the controller 50 can decrease the output voltage VL of thehigh voltage battery 2 from the stationary voltage VH to 0 V within adesired time (the time t2 to a time t3). The controller 50 may regulatea discharge current passing through the FET 13. In this case, thecontroller 50 can limit the discharge current by relatively reducing avoltage to be applied to the gate terminal of the FET 13 (a gate-sourcevoltage) as illustrated in FIG. 5, for example. With this limitation,the controller 50 can inhibit an overcurrent from passing through thepower supply circuit 101 at the time of discharge and can prevent theovercurrent from affecting the FET 13 and the like. Upon completion ofthe discharge of the capacitor C, the controller 50 outputs thedownstream semiconductor drive signal (OFF) to the driver 22 to turn offthe FET 12 (a time t4) and to completely turn off the high voltagesystem 100. From the time t0 to the time t1, the high voltage system 100turns on to make the power supply circuit 101 an energized state. Fromthe time t1 to the time t4, a circuit for discharge turns on to give adischarge state. After the time t4, the high voltage system 100 turnsoff to make the power supply circuit 101 an interrupted state.

Immediately after the collision signal (collision) is output from theexternal device, the semiconductor drive signal (OFF) is output from theexternal device to the controller 50. The reason why the certain time isgiven between the time t1 and the time t2 when thesemiconductor-for-discharge drive signal (ON) is output is to prevent ashort circuit. That is to say, when the operation to turn off the FET 11(the time t1) and the operation to turn on the FET 13 (the time t2) areperformed at the same time, the FET 11 and the FET 13 may simultaneouslyturn on to be short-circuited; the reason is to prevent the shortcircuit.

The following describes an operation example (a short circuit operation)of the semiconductor relay control device 1 with reference to FIG. 6 andFIG. 7. This example assumes that in the high voltage system 100, thepower supply circuit 101 is in an energized state at a time t0. That isto say, in the high voltage system 100, the FETs 11 and 12 turn on, theFET 13 turns off, and the output voltage VL of the high voltage battery2 is the stationary voltage VH. In this case, when a short circuit isdetermined based on the detection current output from the currentdetector 30, the controller 50 of the semiconductor relay control device1 outputs the upstream semiconductor drive signal (OFF) to the driver 21to turn off the FET 11 (a time t1). With this operation, the controller50 makes the power supply circuit 101 an interrupted state. In thisprocess, as illustrated in FIG. 7, in the high voltage system 100, theturning off of the FET 11 may produce a negative surge voltage in thesource terminal of the FET 11. In this case, the controller 50 turns onthe FET 12 and turns off the FET 13, and the negative surge voltage isclamped by the body diode D3 of the FET 13. With this operation, thenegative surge voltage is reduced by the forward voltage of the bodydiode D3 of the FET 13. That is to say, the negative surge voltage isreduced to about a voltage lower than the potential of the negativeelectrode of the high voltage battery 2 illustrated in FIG. 7 by aforward voltage VF of the body diode D3 of the FET 13 (−VF). With thisreduction, the controller 50 can prevent the overvoltage of the negativesurge voltage from affecting the FET 11 and the like. After reducing thenegative surge voltage, the controller 50 outputs the downstreamsemiconductor drive signal (OFF) to the driver 22 to turn off the FET 12(a time t2) and to completely turn off the high voltage system 100. Fromthe time t0 to the time t1, the high voltage system 100 turns on to makethe power supply circuit 101 an energized state. From the time t1 to thetime t2, a circuit for reducing the negative surge voltage turns on togive a state with the negative surge voltage reduced. After the time t2,the high voltage system 100 turns off to make the power supply circuit101 an interrupted state.

FIG. 7 illustrates a negative surge voltage VS when the negative surgevoltage is not clamped by the body diode D3 as a comparative example.This negative surge voltage VS may exceed a semiconductor withstandvoltage. When determining a short circuit, the controller 50 outputs anabnormality (short circuit) detection signal to the external device.After outputting the abnormality (short circuit) detection signal to theexternal device, the semiconductor drive signal (OFF) is output from theexternal device to the controller 50.

As described above, the power supply circuit 101 according to the firstembodiment is a circuit in which the high voltage battery 2 and the highvoltage load part 3 are connected to each other and is a circuit inwhich the capacitor C of the high voltage load part 3 is connected inparallel to the high voltage battery 2. The upstream power supplycircuit 101 a is a circuit between the positive electrode of the highvoltage battery 2 and the high voltage load part 3 in the power supplycircuit 101. The semiconductor relay control device 1 includes the FET11, the FET 12, the FET 13, and the controller 50. The FET 11 isconnected in series to between the positive electrode of the highvoltage battery 2 and the high voltage load part 3 in the upstream powersupply circuit 101 a. The FET 11 turns on to make the upstream powersupply circuit 101 a an energized state and turns off to make theupstream power supply circuit 101 a an interrupted state. The FET 12 isconnected in series to between the negative electrode of the highvoltage battery 2 and the high voltage load part 3 in the downstreampower supply circuit 101 b between the negative electrode of the highvoltage battery 2 and the high voltage load part 3. The FET 12 turns onto make the downstream power supply circuit 101 b an energized state andturns off to make the downstream power supply circuit 101 b aninterrupted state. The FET 13 is connected in parallel to the capacitorC, turns on to make the anode and the cathode of the capacitor C anenergized state, and turns off to make the anode and the cathode aninterrupted state. The controller 50 controls the FET 11, the FET 12,and the FET 13. The controller 50 turns on the FET 11 and the FET 12 andturns off the FET 13 to make the power supply circuit 101 an energizedstate. When a certain discharge request is input in the energized stateof the power supply circuit 101, the controller 50 turns off the FET 11and turns on the FET 12 and the FET 13.

With this configuration, when a request to discharge the capacitor C isinput at the time of abnormality such as a vehicle collision and anelectric leakage, the semiconductor relay control device 1 can quicklydischarge the electric charges charged to the capacitor C via the FET 13and the FET 12, for example. With this discharge, the semiconductorrelay control device 1 can reduce the voltage of the capacitor C withina desired time at the time of abnormality and can thus prevent thecapacitor C from being exposed to the outside in a state of highvoltage. Consequently, the semiconductor relay control device 1 canappropriately address the power supply circuit 101 at the time ofabnormality and can thus improve safety.

In the semiconductor relay control device 1, the controller 50 controlsthe FET 13 to regulate the current passing through the FET 13. With thisconfiguration, the semiconductor relay control device 1 can inhibit anovercurrent from passing through the power supply circuit 101 at thetime of discharge and can thus prevent the overcurrent from affectingthe FET 13 and the like.

The semiconductor relay control device 1 includes the body diode D3 thatis provided so as to have a current passing direction opposite to thedirection in which a current passes from the high voltage battery 2 tothe high voltage load part 3 and is connected in parallel to the sourceterminal and the drain terminal of the FET 13. When the power supplycircuit 101 is short-circuited, the controller 50 turns off the FET 11and the FET 13 and turns on the FET 12. With this configuration, thesemiconductor relay control device 1 can clamp and reduce the negativesurge voltage occurring by the turning off of the FET 11 by the bodydiode D3. With this reduction, the semiconductor relay control device 1can prevent the negative surge voltage from affecting the FET 13 and thelike. The semiconductor relay control device 1 can achieve the reductionin the negative surge voltage and the discharge of the capacitor C byone FET 13 and can thus reduce a parts count. With this reduction, thesemiconductor relay control device 1 can simplify its circuitconfiguration and curb an increase in circuit size. In addition, thesemiconductor relay control device 1 can reduce the cost ofmanufacturing.

Second Embodiment

The following describes a semiconductor relay device 1A according to asecond embodiment. For the second embodiment, components similar tothose of the first embodiment are denoted by the same symbols, and adetailed description thereof will be omitted. The semiconductor relaydevice 1A according to the second embodiment is different from thesemiconductor relay control device 1 according to the first embodimentin that current limitation is performed by a resistor. The semiconductorrelay device 1A according to the second embodiment includes the FET 11,the FET 12, the FET 13, the controller 50, and a precharge circuit 60.The precharge circuit 60 is a circuit limiting current. The prechargecircuit 60 has an FET 14 as a semiconductor relay for precharge, adriver 24, and a resistor R. The precharge circuit 60 forms a seriescircuit 61 in which the resistor R and the FET 14 are connected inseries to each other. The series circuit 61 is connected in parallel tothe FET 12. The FET 14 is a switching element passing or interrupting acurrent passing from the high voltage load part 3 to the negativeelectrode of the high voltage battery 2. The FET 14 is an N-channel typeMOSFET, for example. The FET 14 has a gate terminal, a drain terminal,and a source terminal. The gate terminal of the FET 14 is connected tothe driver 24, the drain terminal thereof is connected to the highvoltage load part 3 via the resistor R, and the source terminal thereofis connected to the negative electrode of the high voltage battery 2. Inthe FET 14, an ON voltage is applied to the gate terminal, whereby acurrent passes between the drain and the source. In the FET 14, an OFFvoltage is applied to the gate terminal, whereby no current passesbetween the drain and the source. The FET 14 is driven by the driver 24to pass a precharge current via the resistor R. The semiconductor relaydevice 1A turns on the FETs 11 and 14 and turns off the FETs 12 and 13to pass a precharge current with the current limited by the resistor Rof the precharge circuit 60, for example. The semiconductor relay device1A turns off the FETs 11 and 12 and turns on the FETs 13 and 14 todischarge the electric charges charged to the capacitor C via theprecharge circuit 60. The semiconductor relay device 1A turns on theFETs 11 and 12 and turns off the FETs 13 and 14 to make the power supplycircuit 101 an energized state. The semiconductor relay device 1A turnsoff the FETs 11 to 14 to make the power supply circuit 101 aninterrupted state.

As described above, the semiconductor relay device 1A according to thesecond embodiment includes the FET 11, the FET 12, the FET 13, theprecharge circuit 60, and the controller 50. The FET 11 is connected inseries to between the positive electrode of the high voltage battery 2and the high voltage load part 3 in the upstream power supply circuit101 a. The FET 11 turns on to make the upstream power supply circuit 101a an energized state and turns off to make the upstream power supplycircuit 101 a an interrupted state. The FET 12 is connected in series tobetween the negative electrode of the high voltage battery 2 and thehigh voltage load part 3 in the downstream power supply circuit 101 bbetween the negative electrode of the high voltage battery 2 and thehigh voltage load part 3. The FET 12 turns on to make the downstreampower supply circuit 101 b an energized state and turns off to make thedownstream power supply circuit 101 b an interrupted state. The FET 13is connected in parallel to the capacitor C, turns on to make the anodeand cathode of the capacitor C an energized state, and turns off to makethe anode and the cathode an interrupted state. The precharge circuit 60has the series circuit 61 in which the resistor R and the FET 14 areconnected in series to each other, with the series circuit 61 connectedin parallel to the FET 13. The precharge circuit 60 passes a currentthrough the series circuit 61 by the turning on of the FET 14 and doesnot pass any current through the series circuit 61 by the turning off ofthe FET 14. The controller 50 controls the FET 11, the FET 12, the FET13, and the precharge circuit 60. The controller 50 turns on the FET 11and the FET 12 and turns off the FETs 13 and 14 to make the power supplycircuit 101 an energized state. When the certain discharge request isinput in the energized state of the power supply circuit 101, thecontroller 50 turns off the FETs 11 and 12 and turns on the FETs 13 and14.

With this configuration, when a request to discharge the capacitor C isinput at the time of abnormality such as a vehicle collision and anelectric leakage, the semiconductor relay device 1A can discharge theelectric charges charged to the capacitor C in a limited manner by theresistor R of the precharge circuit 60, for example. The semiconductorrelay device 1A can pass the precharge current by the precharge circuit60 when the high voltage system 100 is started up.

Modifications

The following describes modifications of the first and the secondembodiments. Although examples in which the N-channel type MOSFET isused for the FETs 11 to 14 have been described, this is not limiting;the FETs 11 to 14 may each be a P-channel type MOSFET, an insulated gatebipolar transistor (IGBT), or a transistor, for example. When asemiconductor relay for discharge having no body diode such as the IGBTor the transistor is used in place of the FET 13, a diode in which aforward current passes from the FET 12 toward the FET 11 is required tobe connected in parallel to the semiconductor relay for discharge.

Although examples in which the semiconductor relay devices 1 and 1A areinstalled in a vehicle have been described, this is not limiting; thesemiconductor relay devices 1 and 1A may be installed in aircraft,ships, buildings, or the like.

The semiconductor relay device according to the present embodiment turnsoff the upstream semiconductor relay and turns on the downstreamsemiconductor relay and the semiconductor relay for discharge when thedischarge request is input and can thus discharge electric chargescharged to the capacitor and appropriately address the power supplycircuit at the time of abnormality.

The semiconductor relay device according to the present embodiment turnsoff the upstream semiconductor relay and the downstream semiconductorrelay and turns on the semiconductor relay for precharge connected tothe resistor and the semiconductor relay for discharge when thedischarge request is input and can thus discharge the electric chargescharged to the capacitor in a limited manner by the resistor andappropriately address the power supply circuit at the time ofabnormality.

Although the invention has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

What is claimed is:
 1. A semiconductor relay control device comprising:an upstream semiconductor relay connected, in an upstream power supplycircuit, in a circuit in which a load part including a capacitor and aDC power supply are connected to each other, the circuit being a powersupply circuit in which the capacitor is connected in parallel to the DCpower supply, between a positive electrode of the DC power supply andthe load part, in series to between the positive electrode and the loadpart, turning on to make the upstream power supply circuit an energizedstate, and turning off to make the upstream power supply circuit aninterrupted state; a downstream semiconductor relay connected, in adownstream power supply circuit between a negative electrode of the DCpower supply and the load part, in series to between the negativeelectrode and the load part, turning on to make the downstream powersupply circuit an energized state, and turning off to make thedownstream power supply circuit an interrupted state; a semiconductorrelay for discharge connected in parallel to the capacitor, turning onto make an anode and a cathode of the capacitor an energized state, andturning off to make the anode and the cathode an interrupted state; adiode that is provided so as to have a current passing directionopposite to a direction in which a current passes from the DC powersupply to the load part and is connected in parallel to thesemiconductor relay for discharge; and a controller controlling theupstream semiconductor relay, the downstream semiconductor relay, andthe semiconductor relay for discharge, wherein the controller turns onthe upstream semiconductor relay and the downstream semiconductor relayand turns off the semiconductor relay for discharge to make the powersupply circuit an energized state and, when the power supply circuit isshort-circuited, the controller turns off the upstream semiconductorrelay and the semiconductor relay for discharge and turns on thedownstream semiconductor relay, a negative surge voltage caused by theturning off of the upstream semiconductor relay is clamped by the diode.2. The semiconductor relay control device according to claim 1, whereinwhen a certain discharge request is input in the energized state of thepower supply circuit, the controller turns off the upstreamsemiconductor relay and turns on the downstream semiconductor relay andthe semiconductor relay for discharge.
 3. The semiconductor relaycontrol device according to claim 1, wherein the controller controls thesemiconductor relay for discharge to regulate a current passing throughthe semiconductor relay for discharge.
 4. The semiconductor relaycontrol device according to claim 2, wherein the controller controls thesemiconductor relay for discharge to regulate a current passing throughthe semiconductor relay for discharge.
 5. A semiconductor relay controldevice comprising: an upstream semiconductor relay connected, in anupstream power supply circuit, in a circuit in which a load partincluding a capacitor and a DC power supply are connected to each other,the circuit being a power supply circuit in which the capacitor isconnected in parallel to the DC power supply, between a positiveelectrode of the DC power supply and the load part, in series to betweenthe positive electrode and the load part, turning on to make theupstream power supply circuit an energized state, and turning off tomake the upstream power supply circuit an interrupted state; adownstream semiconductor relay connected, in a downstream power supplycircuit between a negative electrode of the DC power supply and the loadpart, in series to between the negative electrode and the load part,turning on to make the downstream power supply circuit an energizedstate, and turning off to make the downstream power supply circuit aninterrupted state; a semiconductor relay for discharge connected inparallel to the capacitor, turning on to make an anode and a cathode ofthe capacitor an energized state, and turning off to make the anode andthe cathode an interrupted state; a precharge circuit having a seriescircuit in which a resistor and a semiconductor relay for precharge areconnected in series to each other, the series circuit being connected inparallel to the downstream semiconductor relay, passing a currentthrough the series circuit by the turning on of the semiconductor relayfor precharge, and not passing any current through the series circuit bythe turning off of the semiconductor relay for precharge; a diode thatis provided so as to have a current passing direction opposite to adirection in which a current passes from the DC power supply to the loadpart and is connected in parallel to the semiconductor relay fordischarge; and a controller controlling the upstream semiconductorrelay, the downstream semiconductor relay, the semiconductor relay fordischarge, and the semiconductor relay for precharge, wherein thecontroller turns on the upstream semiconductor relay and the downstreamsemiconductor relay and turns off the semiconductor relay for dischargeand the semiconductor relay for precharge to make the power supplycircuit an energized state and, when the power supply circuit isshort-circuited, the controller turns off the upstream semiconductorrelay and the semiconductor relay for discharge and turns on thedownstream semiconductor relay, a negative surge voltage caused by theturning off of the upstream semiconductor relay is clamped by the diode.6. The semiconductor relay control device according to claim 5, whereinwhen a certain discharge request is input in the energized state of thepower supply circuit, the controller turns off the upstreamsemiconductor relay and the downstream semiconductor relay and turns onthe semiconductor relay for precharge and the semiconductor relay fordischarge.